The war of the personal digital assistants just got hotter. Amazon announced that it’s putting its Alexa voice assistant officially on the iPhone. Alexa is available through Amazon’s iOS shopping app. It is not yet available for Android.

With Alexa joining Microsoft’s Cortana in challenging Siri on Apple’s own turf, it brings up the question for consumers of whether it’s worth installing multiple voice assistants on their iPhones. Answering that question for yourself is easiest if you know the strengths and weaknesses of each assistant.

Let’s start with Alexa. Alexa is most associated with the Echo line of smart speakers, and is best at answering questions, setting timers and performing various skills that users can pick from an ever-growing list of options. Alexa in an Echo can give you a newsflash or control smart appliances in your home.

On the iPhone, however, the assistant’s options are currently more limited. For example, I couldn’t get a news briefing from the Alexa in Amazon’s iPhone app. I couldn’t set a timer either. But other features such as getting answers to questions such as – “Who was the eighth president of the United States?” – do work. Integration with Amazon services works, too, so you’ll be able to ask Alexa to search its website for the products you want.

Microsoft’s Cortana is good for scheduling meetings and reminders that come up during the day. But I’ve found it’s better as a desktop or laptop assistant. On mobile devices, it requires a separate download to get on your phone. That means that you will always have to open the app to use it – at which point you may as well just type in a search.

Which brings us to Siri and its greatest advantage: it is the default personal assistant on the iPhone.